• Thomas Gleixner's avatar
    tick/broadcast: Make idle check independent from mode and config · f32dd117
    Thomas Gleixner authored
    Currently the broadcast busy check, which prevents the idle code from
    going into deep idle, works only in one shot mode.
    
    If NOHZ and HIGHRES are off (config or command line) there is no
    sanity check at all, so under certain conditions cpus are allowed to
    go into deep idle, where the local timer stops, and are not woken up
    again because there is no broadcast timer installed or a hrtimer based
    broadcast device is not evaluated.
    
    Move tick_broadcast_oneshot_control() into the common code and provide
    proper subfunctions for the various config combinations.
    
    The common check in tick_broadcast_oneshot_control() is for the C3STOP
    misfeature flag of the local clock event device. If its not set, idle
    can proceed. If set, further checks are necessary.
    
    Provide checks for the trivial cases:
    
     - If broadcast is disabled in the config, then return busy
    
     - If oneshot mode (NOHZ/HIGHES) is disabled in the config, return
       busy if the broadcast device is hrtimer based.
    
     - If oneshot mode is enabled in the config call the original
       tick_broadcast_oneshot_control() function. That function needs
       extra checks which will be implemented in seperate patches.
    
    [ Split out from a larger combo patch ]
    Reported-and-tested-by: default avatarSudeep Holla <sudeep.holla@arm.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Cc: Suzuki Poulose <Suzuki.Poulose@arm.com>
    Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
    Cc: Catalin Marinas <Catalin.Marinas@arm.com>
    Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
    Cc: Ingo Molnar <mingo@kernel.org>
    Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1507070929360.3916@nanos
    f32dd117
tick-broadcast.c 25.8 KB